#! perl -slw
use strict;
use GD;
GD::Image->trueColor( 1 );
my $im1 = GD::Image->new( $ARGV[ 0 ] );
my $im2 = GD::Image->new( $ARGV[ 1 ] );
my $raw1 = $im1->gd;
my $raw2 = $im2->gd;
my $xored = $raw1 ^ $raw2;
my( $all, $diff ) = (0)x2;
$all += 255, $diff += ord substr $xored, $_, 1 for 0 .. length( $xored ) - 1;
print $all, ' ', $diff;
printf "The simlarity is %.3f%%\n", ( $all - $diff ) / $all * 100;
####
C:\test\xx>..\907337 ballons1.jpg ballons2.jpg
672410265 62443267
The simlarity is 90.714%
##
##
C:\test\xx>..\907337 ballons1.jpg ballons1a.jpg
672410265 92011553
The simlarity is 86.316%
##
##
C:\test\xx>..\907337 1.png 2.png
244802805 241803
The simlarity is 99.901%
##
##
C:\test\xx>..\907337 microarray1.jpg microarray2.jpg
340764405 41409302
The simlarity is 87.848%